Several model building techniques have recently become available for building three-dimensional objects in layers. One such technique is stereolithography, which is described in U.S. Pat. Nos. 4,575,330 and 4,929,402 hereinafter the '330 and the '402 patents), the disclosures of which are hereby fully incorporated by reference herein as though set forth in full. According to the principles of stereolithography, a three-dimensional object is formed layer by layer in a stepwise fashion out of a material capable of physical transformation upon exposure to synergistic stimulation. In one embodiment of stereolithography, layers of untransformed material such as liquid photopolymer or the like are successively formed at the working surface of a volume of the liquid photopolymer contained in a container. The untransformed layers are successively formed over previously-transformed material. The process of forming these untransformed layers is known as a recoating step, and is described in detail in U.S. application Ser. No. 515,479.
Upon formation, the untransformed layers are selectively exposed to synergistic stimulation such as UV radiation, or the like, whereupon they form object layers. Moreover, upon transformation into the object layers, the untransformed layers typically adhere to the previously-formed layers through the natural adhesive properties of the photopolymer upon solidification. Additional details about stereolithography are available in the following co-pending patent applications, all of which, including appendices, are hereby fully incorporated by reference herein as though set forth in full:
______________________________________ U.S. patent application Ser. No. Filing Date Status ______________________________________ 07/182,830 4/18/88 U.S. Pat. No. 5,059,359 07/183,016 4/18/88 U.S. Pat. No. 4,996,010 07/182,801 4/18/88 U.S. Pat. No. 4,999,143 07/183,015 4/18/88 U.S. Pat. No. 5,015,424 07/268,429 11/8/88 U.S. Pat. No. 5,076,974 07/268,837 11/8/88 U.S. Pat. No. 5,123,734 07/268,816 11/8/88 U.S. Pat. No. 5,058,988 07/268,907 11/8/88 U.S. Pat. No. 5,059,021 07/331,644 3/31/89 U.S. Pat. No. 5,184,307 07/339,246 4/7/89 U.S. Pat. No. 5,104,592 07/429,435 10/30/89 U.S. Pat. No. 5,130,064 07/365,444 6/12/89 U.S. Pat. No. 5,143,663 07/427,885 10/27/89 U.S. Pat. No. 5,133,987 07/429,911 10/27/89 U.S. Pat. No. 5,182,056 ______________________________________
In conventional embodiments of a stereolithographic apparatus, the material used is normally flowable so that it can be disposed onto a working surface in preparation for exposure to the synergistic stimulation. Conventional materials which are typically used are photopolymers which solidify upon exposure to UV radiation from a UV laser or the like.
The use of these conventional materials is sometimes problematic, since they can be toxic when placed in contact with the skin, and are also difficult to dispose of easily. The use of UV radiation from UV lasers is also sometimes problematic because of the potential injury to the human eye. As a result, the use of this radiation must be controlled, and precautions taken, to minimize the risk of eye injury. Moreover, the time required for the photopolymers to solidify upon exposure to the UV radiation can be prohibitively long. Finally, these materials are typically very viscous, so that the time required to form a fresh layer of material over the working surface in anticipation of the formation of the next object cross-section can be prohibitively long.
Another problem with conventional stereolithographic apparatus is the difficulty of rapidly substituting materials throughout the part-building process, which would enable different portions of the same part to be formed out of different materials having different properties such as color, conductivity, and the like. Rapid material substitution is difficult in a conventional stereolithography apparatus, since the material used to build the part is typically contained in a container, and it is difficult or time-consuming to be able to substitute different containers throughout part building.
Rapid material substitution, however, would be beneficial. When building part supports, such as web supports described in U.S. Pat. No. 4,999,143, for example, the ability to use a different material for the supports compared with the part would be desirable, because the supports could then be constructed out of a material which could more easily be removed from the part after the part has been built, without damage to the part. At present, in conventional stereolithographic apparatus, the same material is used to build the supports, causing them to adhere strongly to the part. As a result, the subsequent removal of the supports can lead to ripping or tearing of the part.
Consequently, it is an object of the subject invention to provide an apparatus of and method for providing three-dimensional objects through the principles of stereolithography, but which employ the use of normally solid materials which are made flowable upon the application of thermal radiation such as heat. It is a further object to provide such an apparatus which can be coupled to a conventional stereolithographic apparatus. It is a further object to provide a stereolithographic apparatus which enables rapid substitution of materials throughout part building. It is a further object to provide a stereolithographic apparatus for and method of forming three-dimensional objects which enable the use of a different support material from the material used to build the part, which support material is chosen so that it is easily removable from the part.
Additional objects and advantages will be set forth in the description which follows or will be apparent to those of ordinary skill in the art who practice the invention.